Formation flying. A great way to sharpen your flying skills and have lots of
fun in the process - just make sure to get proper instruction.
FFI (Formation Flying Inc.)
issues formation-flying credentials required to fly formation in waivered airspace. I'm an FFI flight lead.
American Yankee Association (AYA) organizes
fun fly-ins, provides useful information about Grumman aircraft (those
with reciprocating engines).